Liquid crystal display devices are being used in watches, calculators, various measurement instruments, automobile panels, word processors, electronic organizers, printers, computers, televisions, clocks, advertising boards, etc. Representative examples of liquid crystal display modes include twisted nematic (TN) mode, super twisted nematic (STN) mode, and vertical alignment mode and in-plane-switching (IPS) mode that use thin film transistors (TFTs). The liquid crystal compositions used in these liquid crystal display devices are required to be stable against external factors such as moisture, air, heat, and light, exhibit a liquid crystal phase in a temperature range as wide as possible around room temperature, have low viscosity, and operate at low drive voltage. The liquid crystal compositions are composed of several to dozens of compounds in order to optimize dielectric anisotropy (Δε) and/or refractive index anisotropy (Δn), etc., for each individual display device.
A vertical alignment (VA) display uses a liquid crystal composition having negative Δε. A horizontal alignment display such as a TN mode, STN mode or in-plane-switching (IPS) mode display uses a liquid crystal composition having positive Δε. Also reported is a drive mode with which a liquid crystal composition with positive Δε is vertically aligned in the absence of voltage and display is conducted by applying a horizontal electric field. The need for liquid crystal compositions having positive Δε is increasing as ever. Meanwhile, low-voltage driving, high speed response, and a wide operation temperature range are required in all driving modes. In other words, positive Δε with a large absolute value, a low viscosity (η), and a high nematic phase-isotropic liquid phase transition temperature (Tni) are required. Moreover, due to setting of Δn×d, namely, the product of Δn and cell gap (d), Δn of the liquid crystal composition must be adjusted to an appropriate level according to the cell gap. In order to apply liquid crystal display devices to televisions and the like, high-speed response is important and thus a liquid crystal composition having a low rotational viscosity (γ1) is required.
As a structure of a high-speed-response-oriented liquid crystal composition, a liquid crystal composition has been disclosed in which a liquid crystal compound represented by formula (A-1) or (A-2) having positive Δε is used in combination with a liquid crystal compound (B) having neutral Δε (PTL 1 to PTL 4).

As usage of liquid crystal display devices expands, large changes have been seen in the way they are manufactured and used. In order to cope with these changes, optimization of properties other than the basic physical property values known in the art has become necessary. In other words, more VA-mode and IPS-mode liquid crystal display devices that use liquid crystal compositions are being used, and super large screen display devices of 50 or more have been introduced into the market and used. As the substrate size increases, the mainstream method for injecting a liquid crystal composition into a substrate has shifted from a conventional vacuum injection method to a one-drop-fill (ODF) method, and this causes a problem of display quality degradation caused by drop marks that occur as the liquid crystal composition is dropped onto the substrate.
Moreover, in a liquid crystal display device production process by the ODF method, the optimum amount of the liquid crystal dropped must be adjusted in accordance with the size of the liquid crystal display device. If the amount dropped significantly deviates from the optimum value, the balance between refractive index and driving electric field of the liquid crystal device preliminarily designed is no longer retained, and display failures such as nonuniformity and contrast failures occur. In particular, small-size liquid crystal display devices widely used in now prevailing smart phones involve a small optimum liquid crystal injection amount, and thus it is difficult to control deviation from the optimum value to be within a particular range. Thus, in order to achieve high yield in producing liquid crystal display devices, the liquid crystal must have properties that can resist impact and sudden pressure fluctuations within a dropping device during dropping of the liquid crystal, and be capable of being stably and continuously dropped over a long period of time.
In sum, a liquid crystal composition used in an active matrix driving liquid crystal display device driven by TFT elements and the like is required to maintain properties and performance, such as high-speed response, required by liquid crystal display devices; furthermore, there are needs for development that further improves stability against external factors such as light and heat (PTL 5 and PTL 6) and achieves high resistivity and high voltage holding ratio which have been previously considered important from the viewpoint of a production method for a liquid crystal display device.